This invention relates generally to devices for interventional therapeutic treatment or vascular surgery for treatment of defects in the vasculature, and more particularly concerns a system and method for delivering a self-expanding braided stent to a treatment site in a vasculature of a patient.
Stents, which are tubular reinforcements inserted into a blood vessel to provide an open path within the blood vessel, have been widely used in intravascular angioplasty treatment of occluded cardiac arteries. In such applications, the stent is inserted after an angioplasty procedure or the like in order to prevent restenosis of the artery. In these applications, the stents are often deployed by use of inflatable balloons, or mechanical devices which force the stent open, thereby reinforcing the artery wall and provide a clear through-path in the center of the artery after the angioplasty procedure to prevent restenosis.
While such procedures may be useful in certain aspects of vascular surgery in which vasoocclusive devices are used, the weakness and tortuosity of the neurovasculature places limits on the applicability of such stents in procedures to repair neurovascular defects. Furthermore, the use of placement techniques, such as balloons or mechanical expansions of the type often found to be useful in cardiac surgery, are relatively less useful in vasoocclusive surgery, particularly when tiny vessels, such as those found in the brain, are to be treated. Hence, those skilled in the art have recognized a need for a stent compatible with techniques in vasoocclusive treatment of neurovascular defects that provides selective reinforcement in the vicinity of a neurovascular defect, while avoiding any unnecessary trauma or risk of rupture to the blood vessel.
Braided stents, typically formed from a plurality of elongate members, such as two or more metal wires, or polymeric fibers or strands of material, for example, can be very useful in treatment of neurovascular defects. However, one of the problems in deploying a self-expanding braided stent in a body lumen is activation of the initially expanding end, typically the distal end of the braided stent, to fully open. It is important that the initially expanding end should open fully, easily, and quickly, so that the rest of the length of self-expanding braided stent can be deployed, using the initially expanding end as an anchor point.
Stents made of braided wire also commonly have a high internal friction that resists the inherent radial expansion force of the self-expanding braided stent to open, particularly resisting opening of the initially expanding end, which can cause problems in anchoring and deployment of such self-expanding braided stents. Another common problem with deployment of braided stents is difficulty in advancing the compressed or crimped braided stent through a delivery sheath or microcatheter, typically also due to friction between the braided stent and the delivery sheath or microcatheter. Traditional delivery systems for braided stents push the braided stent in a distal direction by advancing a blunt surface against a proximal end of the braided stent, and consequently the application of force on the proximal end of the braided stent tends to axially compress the braided stent, causing the braided stent to expand radially. As a result, as the braided stent expands within the delivery sheath or microcatheter, an increased normal force is applied to the inner surface of the delivery sheath or microcatheter, increasing friction between the braided stent and the delivery sheath or microcatheter.
Current self-expanding braided stents typically depend solely on their material, dimension, cell design, and internal friction to expand. Deployment of such self-expanding braided stents commonly requires extra manipulation by a user to fully open the self-expanding braided stents, which affects placement accuracy and adds risk to the procedure. Proper deployment and fixation of the initial deployment end or distal end of a self-expanding braided stent are necessary for the subsequent proper alignment and positioning of the remainder of the stent body.
Another problem with deployment of self-expanding braided stents involves difficulty in recapturing a self-expanding braided stent after partial deployment and prior to full deployment of the stent. Currently, a self-expanding braided stent typically is advanced through a delivery sheath or microcatheter until the self-expanding braided stent emerges. When the self-expanding braided stent is unrestrained outside of the sheath or microcatheter, the self-expanding braided stent typically then expands and is deployed in the vasculature, making recapturing of the self-expanding braided stent difficult.
It would be desirable to provide an improved self-expanding braided stent with increased radial expansion force, particularly at the initial deployment end or distal end, that can also reduce the internal friction of the braided stent during delivery of the braided stent through a delivery sheath or microcatheter, for improved ease and reliability of deployment of the self-expanding braided stent, particularly at the initial deployment end or distal end of the self-expanding braided stent. It also would be desirable to provide an improved self-expanding braided stent that can be recaptured following partial deployment of a distal portion of the self-expanding braided stent prior to full deployment of a later deployed portion or proximal portion of the self-expanding braided stent. The present invention meets these and other needs.